Lateral spine stabilization devices and methods

ABSTRACT

A resilient core is positioned between bony projections which are offset from a principal load bearing region of a spinal joint. Shaped projections extend from the core, and engage the bony projections by conforming to anatomical landmarks, and may be fastened to the bony projections. During flexion of the joint, the core absorbs some of the force of compression, and limits an extent to which the joint may compress. If the shaped projections are connected to the bony projections, extension of the joint is inhibited by the projections and the core, limiting the extent to which the joint may be distracted. In this manner, healing is fostered, and a weakened or damaged joint is protected from excessive movement.

FIELD OF THE INVENTION

This invention relates to stabilizing adjacent vertebrae of the spine,after surgery or trauma, between bone portions at a distance from thevertebral body.

BACKGROUND OF THE INVENTION

Compression of a portion of the spinal cord or nerve root may be causedby trauma to the spine, or by a spinal disorder, for example spinalstenosis, degenerative disc disease, a bulging or herniatedintervertebral disc, bone spurs, spondylosis, or spinal osteoarthritis.Surgery may be conducted upon the affected area to relieve thecompression, however the problem may reoccur prior to complete healing,or due to an ongoing disease process.

Compression of nerve tissue may take place, for example, during bending,and in particular during lateral bending, where the disc annulus isdamaged or weakened. During bending, the flexion side of the disccompresses and the extension side stretches. When the pressure ofcompression exceeds the tissue strength of the annulus, the nucleus maybe extruded through the extension side, where it commonly compressesnerve tissue. This tends to occur more towards the posterior end of thevertebral column.

As an alternative to an anterior approach to the disc or other areas ofthe spine, a posterior approach including a foraminotomy may beperformed to access the spinal cord and impinging tissue, and to relievecompression. During a foraminotomy, bone from the posterior arch of thespine over the nerve, or lamina, and possibly part of the facet joint,is removed using special cutting instruments and/or a drill. Theneuroforamen may be enlarged in some cases to decompress the affectednerve portion. Additionally, portions of the disc may be removed.

Whether an anterior or posterior approach is taken, spine stability maybe compromised due to the removal of supporting tissue, leaving thespine vulnerable to further damage.

SUMMARY OF THE INVENTION

In accordance with the invention, a supporting structure, stanchion, orstrut includes a longitudinal body which is advantageously resilient,and superior and inferior braces connected to and extending from thebody. The strut is sized and dimensioned to be inserted into the body ata location between bony extensions of adjacent vertebrae. The braceseach contact and engage bony extensions of different vertebrae, and areadvantageously shaped to conform to or surround at least a portion ofthe bony extensions.

In one embodiment of the invention, a strut of the invention ispositioned between transverse processes of adjacent vertebrae. It shouldbe understood, however, in accordance with the invention, that the strutmay be positioned between any bony structure of adjacent vertebrae,which extends at a distance from the body of the vertebra, including butnot limited to the pedicles, laminae, and spinous process, as well.

The superior and inferior braces of the strut of the invention may beconfigured to engage a respective extending bone by any known means, andmay have a loose fitting engagement on upper and lower bones.Alternatively, one or both of the braces may be fastened to itsrespective bone, for example by bone screws, adhesive, or a clamp orstrap. In one embodiment, one or both braces may be configured as apost, possibly with threads, which is inserted into a bony extension.

A strut in accordance with the invention may have a reduced height aftercompression during flexion, and if unconnected to bony extensions at thebraces, a strut may have an original height on an extended side of thejoint. If the braces of the invention are connected to the bones,however, a height of the strut may be greater than a resting heightthereof.

In alternative embodiment of the invention, a strut is formed by twolongitudinal panels that are connected by a cross member. The crossmember may advantageously connect the panels at an angle, therebyforming two gaps into each of which a portion of a bony extension mayreside, after implantation. The cross member may alternatively connectto one or both panels perpendicularly. Further, the cross member mayconnect to the panels in a different location upon each panel.

Selection of an attachment angle and location is based upon a general orimaged anatomy of the intended site of implantation. More particularly,bony extensions of the spine are not necessarily linearly aligned;rather, a healthy spine follows a complex curve which places analogousbony extensions at an offset angle with respect to one another.Moreover, the size of bony extensions may differ greatly betweenadjacent vertebrae. Selection of a suitable offset cross member or panelposition enables the practitioner to form a fit which best serves thetherapeutic needs of the individual patient. To enable the practitionerto modify the device during a procedure, the panel may be provided witha plurality of mounting points.

One or more of the panels, or the cross member, may be formed from aresilient material, to provide a desired amount of compression,twisting, and rebound force. The size and stiffness of the panels andcross member may be selected based upon an individual patient's needs,determined from preoperative consultation, examination, and imaging, orduring the procedure. Accordingly, provision of a plurality of sizes andmaterials, and or the provision of suitable instrumentation, may beachieved using a kit.

The strut or panels may be provided with one or more boreholes operativeto admit a screw, pin, or other fastener, whereby the strut or panel maybe fastened to bone.

A strut of the invention may additionally be configurable, whereby thestrut may be implanted in a first configuration, and changed during orafter implantation to a second configuration. A connecting fastener isassociated with the strut body, and is operative to releasably orrotatably connect a configurable panel to the body, whereby the strutmay be more easily manipulated into a position within the body.

A strut of the invention is advantageously positioned adjacent to aresected area, for example a resected lamina, which may have beenweakened, and advantageously but not necessarily an additional strut maybe positioned at an opposite portion of the joint, for example in acorresponding location on an opposite side of the joint. In accordancewith one use of the invention, for example, a foramen that has beentreated, as by enlargement, may be protected from further narrowing.

Struts of the invention may be implanted using open or minimallyinvasive surgical techniques, and may be used in the context ofnon-instrumented procedures, as well as in combination with otherimplants, as would be understood by one skilled in the art.

A strut body, panel, or brace of the invention may be regularly shaped,or may be provided with one or more shaped or contoured engagingsurfaces which conform to, and thereby interlock or engage with,existing or created anatomical landmarks. In this manner, the stabilityof the strut is improved, and the potential for migration of the strutfrom an intended location is reduced.

A strut of the invention advantageously includes one or more layersoperative to provide additional functionality. In one embodiment, alayer has a different modulus of elasticity as compared with theremainder of the body, enabling complex damping or reboundcharacteristics. Additionally or alternatively, a layer may include atherapeutic substance, such as one or more of bone growth,antimicrobial, healing, or drug agents.

In accordance with an embodiment of the invention, a strut limitsdistraction of the joint during extension, by exerting a limiting forceat a location at a distance from the body of the joint. The strut mayadvantageously be sized and shaped to weakly resist compression ortwisting. As such, the joint has a greater range of motion, whereneeded.

Struts of the invention are advantageously formed with a flexiblematerial, so that a limit of distraction is arrived at gradually, in aseemingly natural manner, rather than presenting an abrupt limit to arange of motion.

In another embodiment, a strut is passed or looped around the laminae,pedicles, spinous processes, or transverse processes, of adjacentvertebrae. Where there is no natural gap, or it is desired to avoidresecting a gap, the strut may be formed from a flexible strand, withends joined within the body.

Devices of the invention are advantageously used in a context ofnon-instrumented joint stabilization, particularly as they may providefor sufficient stabilization to enable effective and timely fusion.

In accordance with the foregoing, struts of the invention areadvantageously positioned at a distance from the vertebral body, orother weight bearing portion of the vertebral joint, and thus work toprovide a laterally positioned stabilization for damaged or weakenedjoints. By being positioned laterally, struts of the invention benefitfrom added leverage attributable to being a distance from a fulcrum ofthe joint. Leverage is further improved by exploiting existing anatomy,such as the transverse process, to produce leverage at a distance from afulcrum of the joint. As such, a device of the invention may be smallerthan a device that stabilizes from within the vertebral body, and iseasier to implant, with less trauma to the patient. Additionally,devices of the invention are advantageously implanted from a posteriorapproach, which is safer for the patient, and simpler for thepractitioner. Moreover, implantation at a distance from a fulcrum of thejoint concomitantly increases a working distance from the spinal cord,improving safety to the patient.

In accordance with one embodiment of the invention, a device is providedfor stabilization of a joint having a weight bearing fulcrum, and bonyextensions on different vertebrae extending away from the fulcrum. Thedevice comprises a resilient core positionable between the bonyextensions, operative to absorb a compressive force imparted to the coreby the bony extensions, the force arising from flexion of the joint; anda shaped extension connected to the core, operative to engage a shape ofthe bony extensions, thereby stabilizing a position of the core; wherebythe core and the shaped extension cooperate to promote a therapeuticmaximum amount of joint movement.

In embodiments of the invention, the core and the shaped extension fitcompletely between the bony extensions; there are two of the shapedextensions, one of which is operative to engage a posterior face of onebony extension, and the other of which is operative to engage ananterior face of the other bony extension; there are two of the shapedextensions, one of which is operative to engage a superior face of onebony extension, and the other of which is operative to engage aninferior face of the other bony extension; a shaped extension isconnected to a bony extension; a shaped extension is changeable withrespect to the core, whereby implantation of the device is facilitated;the shaped extension is integrally formed with the core, and completelysurrounds the bony extension; the device is positionable between bonyextensions selected from the group consisting of lamina, pedicle,transverse process, articular process, spinous process, lateral massjunction, and inter-posterior arch; the core or shaped extension isfabricated from a material selected from the group consisting of:polymer, PEEK, HMWPE, metal, titanium alloy, chrome alloy, bonesubstitute material, natural material, bone, bone graft material,lyophilized tissue, autograft tissue, allograft tissue, xenografttissue; the core or the shaped extension is provided with layers eachhaving a different modulus of elasticity; the core or shaped extensionis provided with a layer providing a therapeutic benefit selected fromthe group consisting of: bone growth promoting, antimicrobial, healing,therapeutic drug; the core is connected to the bony extensions, wherebythe device is operative to impart a resistive force to distraction ofthe joint; the device is operative to impart a resistive force tocompression of the joint; the core is connected to the bony extensions,and whereby the device is operative to impart both a resistive force todistraction of the joint, and a resistive force to compression of thejoint; the resistive force to compression is different than theresistive force to distraction; and a plurality of devices are implantedwithin a joint.

In another embodiment of the invention, a device is provided forlimiting movement of a joint of the spine, the joint having a principalweight bearing region and bony projections on each vertebra of thejoint, the bony projections positioned at a distance from the principalweight bearing region, the device comprising a resilient corepositionable to fit completely between a superior portion of the bonyprojection of one vertebra of the joint, and an inferior portion of thebony projection of the other vertebra of the joint; and at least oneshaped extension connected to the core, sized and shaped to engage ananatomical landmark of at least one of the bony projections, therebyoperative to affix a position of the core with respect to the joint;whereby flexion of the joint moves one bony projection closer to theother bony projection, thereby compressing the core, whereby a resistiveforce to compression is imparted by the core to the joint.

In various embodiments, there are two of the shaped extensions, each ofthe shaped extensions connected to a different bony projection by meansselected from the group consisting of: bone screw, screw, adhesive,clamp, strap, pin, suture, and knot; and extension of the joint movesone bony projection further away from the other bony projection, therebyextending the core in connection with the shaped extensions, whereby aresistive force to distraction is imparted by the core to the joint.

In yet another embodiment of the invention, a device is provided forlimiting movement of a joint of the spine, the joint having a principalweight bearing region and bony projections on each vertebra of thejoint, the bony projections positioned at a distance from the principalweight bearing region, the device comprising a resilient corepositionable to fit completely between a superior portion of the bonyprojection of one vertebra of the joint, and an inferior portion of thebony projection of the other vertebra of the joint; and two shapedextensions connected to the core, each sized and shaped to engage ananatomical landmark upon a bony projection of a different vertebra,thereby operative to affix a position of the core with respect to thejoint, at least one of the shaped extensions movably connected to thecore and operative to change an orientation of the shaped extension withrespect to the core, whereby implantation of the device is facilitated;whereby flexion of the joint moves one bony projection closer to theother bony projection, thereby compressing the core, whereby a resistiveforce to compression is imparted by the core to the joint. In onealternative, at least one movably connected extension is rotatablyconnected to the core.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention, and theattendant advantages and features thereof, will be more readilyunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings wherein:

FIG. 1 depicts a cervical spine section of the human body;

FIG. 1a depicts a thoracic spine section of the human body;

FIG. 1b depicts a lumbar spine section of the human body;

FIG. 2 depicts a strut in accordance with the invention;

FIG. 3 illustrates a perspective view of two of the struts of FIG. 2,implanted in a stylized depiction of a vertebral joint;

FIG. 4 shows forces acting upon a bending joint of the spine;

FIG. 5 shows the bending joint of FIG. 4, provided with two of thestruts of FIG. 2, illustrating a change in acting forces;

FIG. 6 depicts an alternative strut in accordance with the invention;

FIG. 7 illustrates two of the struts of FIG. 6, implanted betweenvertebrae;

FIG. 8 illustrates a stylized depiction of adjacent vertebra, showing apositioning of a strut in accordance with FIG. 6;

FIG. 9 illustrates a section of configurable strut in accordance withthe invention, implanted within the body;

FIG. 9A depicts the strut of FIG. 9, configured for implantation;

FIG. 10 illustrates a resection of a vertebra, stabilized by analternative strut in accordance with the invention;

FIG. 10A depicts further detail of the strut of FIG. 10;

FIG. 11 illustrates two of an alternative strut in accordance with theinvention, implanted in connection with cervical vertebrae C1 and C2;and

FIG. 11A depicts further detail of the strut of FIG. 11.

DETAILED DESCRIPTION OF THE INVENTION

In the description which follows, any reference to direction ororientation is intended primarily and solely for purposes ofillustration and is not intended in any way as a limitation to the scopeof the present invention. Also, the particular embodiments describedherein are not to be considered as limiting of the present invention.

Referring now to the figures, in which like reference numerals refer tolike elements, FIGS. 1 and 1B depict schematic illustrations ofcervical, thoracic, and lumbar sections of a vertebral joint 10,respectively, of a spinal column, for reference purposes. Theillustrations show the lamina 12, pedicle 14, body 16, superiorarticular process 18 of the facet joint, spinal cord 20, nerve root 22,spinous process 24, transverse process 26, and foramen 28. As usedherein, reference 26 applies to the transverse process, or any otherbony extension or projection, generally. It should be understood thatthe devices of the invention may be sized and shaped, as would beunderstood by one skilled in the art, to be used with any vertebraltype.

With reference to FIG. 2, in accordance with the invention, a supportingstructure, stanchion, or strut 100 includes a longitudinal body 110which is advantageously resilient, and superior and inferior braces 112,114, connected to and extending from body 110. Strut 100 is sized anddimensioned to be inserted into the body at a location between bonyextensions or projections of adjacent vertebrae. Braces 112, 114 eachcontact and engage bony extensions of different vertebrae, and areadvantageously shaped to conform and or surround at least a portion ofthe bony extensions, thereby to better retain a desired position inrelation thereto.

In one embodiment of the invention, as shown in the diagrammaticperspective illustration of FIG. 3, strut 100 is positioned betweentransverse processes 26 of adjacent vertebrae. It should be understood,however, in accordance with the invention, strut 100 may be positionedbetween any bony structure of adjacent vertebrae, which extends at adistance from the body of the vertebra, including but not limited to thepedicles, laminae, and spinous process, as well. Moreover, strut 100 maybe positioned between differing bony structures of adjacent vertebrae.

In the illustration of FIGS. 2 and 3, strut 100 is depicted as generallyelongated; however a thickness “A” may be wider than what is shown, toincrease stability and strength, according to the best therapeuticinterests of the patient. Similarly, overall height “B” is selected foran optimal fit, as further described herein, wherein a height “B” may beselected to impart no biasing force, or alternatively a predeterminedamount of biasing force, when the vertebral joint is neither flexed norextended. Height “C” of superior or inferior brace 112, 114, and overallwidth “D”, as well as the shape of brace 112, 114, is selected to bestconform to the bone to which the respective brace 112, 114 is to beengaged, to improve stability and reduce the potential for migration.Braces 112, 114 may additionally be provided with shapes that engagelandmarks which are introduced by the practitioner.

Superior and inferior brace 112, 114 may be configured, in accordancewith the invention, to engage a respective extending bone by any knownmeans, including, as illustrated in FIG. 3, a loose fitting engagementon upper and lower bones. Alternatively, one or both of braces 112, 114may be fastened to its respective bone, for example by bone screws,adhesive, or a strap. In one embodiment, one or both of brace 112, 114may be configured as a post, possibly with threads, which is insertedinto a bony extension.

With reference now to FIG. 4, a stylized pair of adjacent vertebraeillustrates forces during joint movement, in vivo. Force arrows P1illustrate compressive forces acting upon a side of the vertebral bodywhen the side is flexed along the line indicated as “E”. It can be seenthat compressive force P1 acts upon disc 30 to shorten a portion 32 ofdisc 30 and thereby cause a lateral displacement of disc materialindicated by arrows L1. When a disc is weakened by trauma or disease,this lateral displacement may become excessive, or the disc annulus mayrupture, releasing a portion of the nucleus pulposus material, resultingin pressure upon a nerve root 22. Accordingly, use of strut 100 inaccordance with the invention reduces the extent of bending, and orreduces the rate of bending, resulting in a reduced severity of discdeformation, and a reduction of pain. Additionally, use of strut 100 maybe beneficial when it is desired to reduce or at least partially preventbending, as during healing from treatment for disc herniation, forexample. A strut in accordance with the invention may additionally beused in conjunction with known annulus repair devices.

Referring now to FIG. 5, struts 100A and 100B have been positionedbetween bony extensions 26 of two adjacent vertebrae. In FIG. 5, twostruts 100A, 100B have been positioned between the adjacent vertebrae,although it should be understood that a therapeutic benefit may beobtained using only a single strut 100, advantageously but notnecessarily positioned on a damaged side of a vertebra. In FIG. 5,during flexion, strut 100A is compressed by a shortening of a distancebetween bony projections 26 on a left side of the drawing. Thus, a forceillustrated as P2′ is applied to strut 100A, causing a reduction incompression force P2 as compared with force P1 of FIG. 4. Alternativelystated, force P2 is reduced due to the absorption of a portion of thetotal force imparted due to flexion, by strut 100A, resulting in areduction or amelioration of the impact of flexion upon disc 30, and inparticular, a reduction in a force of extrusion of disc portion 32. Moreparticularly, the disc extrusion force at L2 of FIG. 5 is less than thatof L1 of FIG. 4, due to the stabilization of strut 100A.

Strut 100A has a reduced height H2 after compression during flexion, andif unconnected to bony extensions 26 at braces 112, 114, an originalheight H1 on an extended side of the joint. If braces 112, 114 areconnected, however, a height of strut 100B may be greater than a restingheight thereof.

With further reference to FIGS. 4 and 5, on the extended side of thejoint, a separating force P3 is exerted upon disc 30. If strut 100B isnot fastened at bony extensions 26, extension will not be inhibited.However, should it be desired to limit extension, for example to fosterthe preservation of a degenerating disc, strut 100A and or 100B may befastened to its respective bony extension. Accordingly, a stretchingforce (not shown) imparted to a strut 100 thus affixed, would produce aproportionate reduction in a force of extension imparted to disc 30.

In FIGS. 6 and 7, an alternative embodiment of the invention isillustrated as strut 120, which includes two longitudinal panels 122,connected by a cross member 124. In the illustrations, cross member 124connects panels 122 at an angle, thereby forming two gaps 126 into eachof which a portion of a bony extension may reside, after implantation,as illustrated in FIGS. 7-9. In the examples shown, panels 122 and crossmember 124 form a shape akin to the letter “N”. Cross member 124 mayalternatively connect to one or both panels 122 perpendicularly. Furthercross member 124 may connect to panels 122 in a different location uponeach panel.

Selection of an attachment angle and location is based upon a general orimaged anatomy of the intended site of implantation. More particularly,bony extensions of the spine are not necessarily linearly aligned;rather, a healthy spine follows a complex curve which places analogousadjacent bone extensions at an offset angle with respect to one another.Moreover, the size of bony extensions may differ greatly betweenadjacent vertebrae. Selection of a suitable offset cross member 124 orpanel 122 position enables the practitioner to form a fit which bestserves the therapeutic needs of the individual patient. To enable thepractitioner to modify the device during a procedure, panel 122 may beprovided with a plurality of mounting points 128, through which afastener may pass. Other adjustable means of attaching either or bothpanels 122 to cross member 124 may be provided, as would be understoodby one skilled in the art.

One or more of panels 122, or cross member 124, may be formed from aresilient material, to provide a desired amount of compression,twisting, and rebound force. The size and stiffness of panels 122 andcross member 124 may be selected based upon an individual patient'sneeds, determined from preoperative consultation, examination, andimaging, or during a therapeutic procedure. Accordingly, provision of aplurality of sizes and materials, and or the provision of suitableinstrumentation, may be achieved using a kit.

FIG. 8 illustrates a stylized pair of adjacent cervical vertebrae, inperspective, showing a position of strut 130 disposed between adjacentlaminae. While cervical vertebrae are illustrated, it should beunderstood that strut 130 may be used with any adjacent vertebrae havingadjacent bones between which an appropriately sized strut 130 may bepositioned. Strut 100 may also be positioned as illustrated in FIG. 8,or either strut 100, 130 may alternatively or additionally be disposedbetween adjacent pedicles 14, or as detailed previously, between anyadjacent bones extending from body 16. Alternatively, a combination ofany of the struts in accordance with the invention may be used within asingle patient.

FIG. 9 illustrates a stylized pair of adjacent bony extensions 26,comprising an outer cortical layer 34, and an inner cancellous layer 36.Strut 130 in accordance with the invention has been implanted betweenbony extensions 26, and is sized and shaped to conformingly engage bonyextensions 26 within gaps 136 during at least a portion of the range ofmovement thereof. Strut 130 additionally illustrates grasping apertures138 which may be formed within a surface of a strut in accordance withthe invention, sized and shaped to engage an implantation ormanipulation tool (not shown).

Strut 130 further illustrates one or more boreholes 140, advantageouslycountersunk, each operative to admit screw, pin or other fastener,whereby strut 130 may be fastened to bone, for example to bony extension26. Such boreholes may additionally or alternatively be provided in oneor more panels. All devices in accordance with the invention may be soadapted, to increase stability of the joint and/or the device, and toprevent migration of the device.

Strut 130 additionally illustrates a configurable fastener in accordancewith the invention, whereby a strut of the invention may be implanted ina first configuration, and changed during or after implantation to asecond configuration. A connecting fastener 144 associated with body 134is provided, operative to releasably or rotatably connect a configurablepanel 146 to body 134. In one embodiment, as illustrated in FIGS. 9 and9A, panels 146 and 132 may be rotated relative to each other, asindicated by arrow “G”, for example, whereby strut 130 may be moreeasily manipulated into a position within the body.

Referring now to FIG. 10, a schematic illustration of a spinal sectionincludes a resected area 40 of lamina 12 and a portion of superiorarticular process 18 or another part of facet joint 38, and a portion ofbody 16. In this example, the resected area provides additional spacefor nerve root 22. It is desired to maintain this additional space overtime, to prevent recurrence of adverse symptoms, due to, for example,further degeneration of adjacent bones. Accordingly, strut 150 of theinvention is advantageously positioned adjacent to the resected area,which may have been weakened, and advantageously but not necessarily atan opposite portion of the joint, for example in a correspondinglocation on an opposite side of the joint. In accordance with one use ofthe invention, for example, a foramen that has been treated, as byenlargement, may be protected from further narrowing.

Struts of the invention may be implanted using open or minimallyinvasive surgical techniques, and may be used in the context ofnon-instrumented procedures, as well as in combination with otherimplants, as would be understood by one skilled in the art.

Strut 150, further illustrated in FIG. 10A, comprises a body 160operative to be positioned upon a bony extension. Strut 150 thereby morereadily fits between adjacent bony extensions where there is verylimited space, for example between pedicles 14, as illustrated, orbetween lamina 12, or between transverse processes 26 which arevestigial. Strut body 160 may be regularly shaped, or as in theembodiment shown in FIG. 10A, may be provided with one or more shaped orcontoured engaging surfaces 164 which conform to, and thereby interlockor engage with, existing or created anatomical landmarks. In thismanner, the stability of strut 150 is improved, and the potential formigration of strut 150 from an intended location is reduced.

Strut 150 advantageously includes one or more layers 162 operative toprovide additional functionality to strut 150. In one embodiment, layer162 has a different modulus of elasticity as compared with body 160,enabling complex damping or rebound characteristics. Additionally oralternatively, layer 162 may include a therapeutic substance, such asone or more of bone growth, antimicrobial, healing, or drug agents. Thelayered structure shown and described for strut 150 may be applied toall struts of the invention.

With reference to FIG. 11, in accordance with the invention, strut 170limits distraction of the joint during extension, by exerting a limitingforce at a location at a distance from the body of the joint. Strut 170,in the embodiment of FIG. 11, is sized and shaped to weakly resistcompression or twisting. As such, the joint between the C1 and C2cervical vertebrae, or atlas 42 and axis 44, as illustrated, isparticularly well suited to the use of strut 170, as a greater range ofmotion is typically desired therebetween. Strut 170 may also be used inother joint locations in the body, where it is desired to limit adistraction or separation of joint components, while providing lesserinhibition of other movements.

Strut 170 is advantageously formed with a flexible material, so that alimit of distraction is arrived at gradually, in a seemingly naturalmanner, rather than presenting as an abrupt limit to a range of motion.

Additionally, as with other struts of the invention, a single strut 170may be used, to provide stabilization for a weakened portion of a joint.Alternatively, two, three, or more struts may be used, at a single jointlevel, or in multiple joints.

While the embodiment shown in FIG. 11 is thin and is intended to weaklyresist compression, it should be understood that strut 170 may besufficiently thick and or rigid to significantly resist compression ortwisting, and may accordingly be fastened to upper and lower boneportions of the joint, using any known means, including clamps, screws,pin, adhesive, suturing, and knotting.

In FIG. 11, strut 170 is passed around laminae 22 of adjacent vertebrae42, 44; however, strut 170 may alternatively be looped over adjacentpedicles, spinous processes, or transverse processes, for example. Wherethere is no natural gap, or it is desired to avoid resecting a gap,strut 170 may be formed from a flexible strand, with ends 172, 174joined within the body. In one embodiment, a coupling 176 surrounds ends172, 174, and is bonded in place, or ends 172, 174 are bonded to eachother, by knotting, crimping, suturing, adhering, brazing, annealing, orany other method known in the art.

A strut 100, 130, 150, or 170 in accordance with the invention, may becombined with other stabilizing means. An example is illustrated in FIG.11, in which flexible stabilization spacers 200, 202 have beenpositioned within the lateral mass junction and the inter-posterior archof C1-C2 (42, 44), respectively. In accordance with the invention, adevice of the invention is positioned at a junction located at adistance from the vertebral body; however atlas 42 uniquely has no body.Accordingly, in the example of FIG. 11, strut 170 is positioned at ajunction located at a distance from a major or principal weight bearingportion of the joint. In this manner, strut 170 fulfills the role ofpreventing hyperextension of the unstable joint, and as described above,possibly resistance to compression as well, while the stabilizationspacers are further operative to maintain a correct range of jointspacing at rest, and during movement.

Devices of the invention are advantageously used in a context ofnon-instrumented joint stabilization, particularly as they may providefor sufficient stabilization to enable effective and timely fusion.

Strut 170 may be fabricated from, or fabricated using, wire, cord, orcable, as a single or multiple strand, whose strands may be joined byany known means, including adhesion, coating, or weaving. Strut 170 mayadditionally be coated with one or more therapeutic layers, which mayinclude bone growth, antimicrobial, or healing agents, or therapeuticdrugs. Strut 170 may additionally be formed with layers of differingstiffness, as described for strut 150.

In accordance with the foregoing, struts of the invention areadvantageously positioned at a distance from the vertebral body 16, orother such principal weight bearing portion of the vertebral joint, andthus work to provide a laterally positioned stabilization for damaged orweakened joints. By being positioned laterally, struts of the inventionbenefit from added leverage attributable to being a distance from afulcrum of the joint. Leverage is further improved by exploitingexisting anatomy, such as the transverse process, to produce leverage ata distance from a fulcrum of the joint. As such, a device of theinvention may be smaller than a device that stabilizes from within thevertebral body, and is easier to implant, with less trauma to thepatient. Additionally, devices of the invention are advantageouslyimplanted from a posterior approach, which is safer for the patient, andsimpler for the practitioner. Moreover, implantation at a distance froma fulcrum of the joint concomitantly increases a working distance fromthe spinal cord, improving safety to the patient.

Devices of the invention, including struts 100, 130, 150 and 170, may befabricated using any biocompatible material having the requisitestrength, durability, and flexibility, including polymers, such as PEEKor HMWPE, metals, such as titanium or chrome alloys, bone substitutematerial, and natural materials, such as bone or bone graft material,including lyophilized tissue, and autograft, allograft, or xenografttissue. Additionally, devices in accordance with the invention may befabricated from a material that biodegrades in the body during atherapeutically advantageous time interval.

Devices of the invention, including struts 100, 130, 150, and 170, areadvantageously provided with smooth and or rounded surfaces, whichreduce a potential for deleterious mechanical effects on neighboringtissues.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed herein above. In addition, unless mention was made above tothe contrary, it should be noted that all of the accompanying drawingsare not to scale. A variety of modifications and variations are possiblein light of the above teachings without departing from the scope andspirit of the invention.

All references cited herein are expressly incorporated by reference intheir entirety. In addition, unless mention was made above to thecontrary, it should be noted that all of the accompanying drawings arenot to scale. There are many different features to the present inventionand it is contemplated that these features may be used together orseparately. Thus, the invention should not be limited to any particularcombination of features or to a particular application of the invention.Further, it should be understood that variations and modificationswithin the spirit and scope of the invention might occur to thoseskilled in the art to which the invention pertains. Accordingly, allexpedient modifications readily attainable by one versed in the art fromthe disclosure set forth herein that are within the scope and spirit ofthe present invention are to be included as further embodiments of thepresent invention.

What is claimed is:
 1. A device for stabilization of a joint, the devicecomprising: a strut having a first portion a second portion, the firstportion and the second portion capable of being rotated with respect toeach other, wherein the first portion comprises a panel and a bodyextending along a longitudinal axis, the body having an upper surfaceangled relative to the longitudinal axis and a lower surface angledrelative to the longitudinal axis, wherein the angled upper surface andthe angled lower surface are parallel to one another, wherein the panelhas a height greater than the body, wherein the panel is fixed inposition relative to the body, and wherein the panel is configured toattach to adjacent bony extensions; a connecting fastener extendingalong the longitudinal axis for connecting the first portion to thesecond portion, wherein the first portion or the second portion isrotated about the longitudinal axis; wherein the strut is positionablebetween the adjacent bony extensions comprising a superior bonyextension and an inferior bony extension, wherein the panel comprises afirst borehole and a second borehole, wherein the first borehole isangled in an upward direction and the second borehole is angled in adownward direction, wherein the first borehole is configured to receivea first fastener to secure the first portion to the superior bonyextension and the second borehole is configured to receive a secondfastener to secure the first portion to the inferior bony extension,wherein the first portion and the second portion each include at leastone grasping structure for engagement with a tool, wherein the firstborehole and the second borehole are countersunk into the first portion.2. The device of claim 1, wherein the first portion is operative toengage a posterior face of the superior bony extension, and the secondportion is operative to engage an anterior face of the inferior bonyextension.
 3. The device of claim 1, wherein the first portion isoperative to engage a superior face of one bony extension, and thesecond portion is operative to engage an inferior face of the other bonyextension.
 4. The device of claim 1, wherein said device is positionablebetween bony extensions selected from the group consisting of lamina,pedicle, transverse process, articular process, lateral mass junction,and inter-posterior arch.
 5. The device of claim 1, wherein said strutis fabricated from a material selected from the group consisting of:polymer, PEEK, HMWPE, metal, titanium alloy, chrome alloy, bonesubstitute material, natural material, bone, bone graft material,lyophilized tissue, autograft tissue, allograft tissue, xenografttissue.
 6. The device of claim 1, wherein said strut is provided withlayers each having a different modulus of elasticity.
 7. The device ofclaim 1, wherein said strut is provided with a layer providing atherapeutic benefit selected from the group consisting of: bone growthpromoting, antimicrobial, healing, therapeutic drug.
 8. The device ofclaim 1, wherein said strut is operative to impart a resistive force todistraction of the joint.
 9. The device of claim 1, wherein said strutis operative to impart a resistive force to compression of the joint.10. The device of claim 1, wherein said strut is operative to impartboth a resistive force to distraction of the joint, and a resistiveforce to compression of the joint.
 11. The device of claim 10, whereinsaid resistive force to compression is different than said resistiveforce to distraction.
 12. A device for stabilization of a joint, thedevice comprising: a strut having a first portion a second portion,wherein the first portion comprises a panel and a body extending along alongitudinal axis, the body having an upper surface angled relative tothe longitudinal axis and a lower surface angled relative to thelongitudinal axis, wherein the angled upper surface and the angled lowersurface are parallel to one another, wherein the panel and the body forman angle relative to one another, wherein the panel is fixed in positionrelative to the body, and wherein the panel is configured to attach toadjacent bony extensions; a connecting fastener for connecting the firstportion to the second portion; wherein the strut is positionable betweenthe adjacent bony extensions comprising a superior bony extension and aninferior bony extension, wherein the first portion comprises a firstborehole and a second borehole, wherein the first borehole is configuredto receive a first fastener to secure the first portion to the superiorbony extension and the second borehole is configured to receive a secondfastener to secure the first portion to the inferior bony extension,wherein the first borehole is angled in an upward direction and thesecond borehole is angled in a downward direction, wherein the firstborehole and the second borehole are countersunk into the first portion.13. The device of claim 12, wherein the first portion is operative toengage a posterior face of the superior bony extension, and the secondportion is operative to engage an anterior face of the inferior bonyextension.
 14. The device of claim 12, wherein the first portion isoperative to engage a superior face of one bony extension, and thesecond portion is operative to engage an inferior face of the other bonyextension.
 15. The device of claim 12, wherein said strut is operativeto impart both a resistive force to distraction of the joint, and aresistive force to compression of the joint.
 16. The device of claim 12,wherein said strut is provided with layers each having a differentmodulus of elasticity.
 17. The device of claim 12, wherein said strut isoperative to impart a resistive force to compression of the joint. 18.The device of claim 17, wherein said resistive force to compression isdifferent than a resistive force to distraction.